HVAC stands for Heating, Ventilation, and Air Conditioning. HVAC systems are the systems that control the temperature, humidity, and air quality of indoor spaces. These systems use a combination of heating, cooling, air circulation, and air filtration to create comfortable indoor environments. The most common type of HVAC system is a split system, which includes an outdoor air conditioner and an indoor furnace. Other types of HVAC systems include heat pumps, geothermal systems, and packaged systems. I write concise books, enjoy and please share.